The present invention relates to a magnetic disk apparatus used for external storage apparatuses of computer systems or the like.
With recent increase in quantity of information, importance of magnetic disk apparatuses as external storage apparatuses is more and more enhanced, and they are always required to have recording capacity of high density.
A magnetic disk apparatus has a magnetic recording medium 1 and a magnetic head 2 (hereinafter referred to as "head") as main constituent elements and further comprises a rotation controlling mechanism 3 of the magnetic recording medium 1, a positioning mechanism 4 for the head 2 and a processing circuit 5 for recorded and reproduced signals. At the time of stopping of the magnetic disk apparatus, the head rests on the magnetic recording medium, and, upon starting of the magnetic disk apparatus, moves above the magnetic recording medium at a very small flying height from the magnetic recording medium or in the state of direct or indirect contact with the magnetic recording medium, thereby to carry out recording and reproducing of information.
In general, in a magnetic disk apparatus, the information is recorded in a large number of tracks provided concentrically or spirally on the magnetic recording medium. In order to improve recording density, it becomes necessary to increase information density in the tracks in circumferential direction (linear recording density). The linear recording density depends on characteristics of magnetic film (coercive force, thickness, etc.) of the magnetic recording medium, head characteristics (frequency characteristics, gap length, etc.) and spacing between the magnetic film of the magnetic recording medium and the head. Recently, this spacing between the head and the magnetic recording medium (herein-after referred to as "flying height") is sharply reduced and is generally 0.05-0.1 .mu.m. In general magnetic disk apparatuses, it is known that both the magnetic head and the magnetic recording medium are worn in the state of the flying height being very small or in the case of the magnetic recording medium and the head directly or nearly contacting with each other, and this wear causes rupture of information to reduce reliability.
Conventionally, the wear is diminished by forming a film of lubricant such as perfluoro polyether or forming a protective film on the surface of the magnetic head. However, these conventional methods are not satisfactory for the diminishment of the flying height of the future magnetic heads, and further intensive improvement is being attempted.
For example, according to IEEE Transaction on Magnetics, Vol. MAG-23, No.5, pp2386 September, 1987, it is attempted to diminish the frictional force and wear by dispersing spherical fine particles of melamine cyanurate (MCA) in the lubricant on the surface of the magnetic disk medium.
As another method, Advances in Information Storage and Processing Systems ASME, ISPS-Vol.1, pp117, 1995 discloses incorporation and dispersion of a phosphazene ring substituted with fluorinated benzene at a terminal (a spherical molecule or soccer ball-shaped molecule of about 1.2 nm in molecular simulation) in the lubricant film on the disk.
Furthermore, Japan Tribology Society, preliminary lecture collection, 1996-10 (page 205) reports to coat on a magnetic recording medium a spherical lubricant such as a polyester hyperbranch polymer substituted with fluorinated carbon at a terminal.
Moreover, as an example of forming a texture on the magnetic head, Japan Tribology Society, preliminary lecture collection, 1996-5 (page 50) proposes a texture of hexagonal honeycomb structure.
The conventional technique disclosed in the above IEEE Transaction on Magnetics gives no consideration to the texture of a slider surface of the magnetic head, the particle size of MCA and the surface roughness of magnetic disk medium, and this technique suffers from the problem that reliability of magnetic disk apparatus performing recording and reproduction at a small floatation distance cannot be ensured.
The conventional technique disclosed in the above Advances in Information Storage and Processing Systems ASME, ISPS gives no consideration to the roughness of magnetic disk medium and the texture of slider surface of the magnetic head and suffers from the problem that reliability of magnetic disk apparatus performing recording and reproduction at a small floatation distance cannot be ensured.
Furthermore, the conventional technique disclosed in the Japan Tribology Society, preliminary lecture collection, 1996-10 (page 205) uses only a spherical lubricant as a lubricant and does not use as additives to a liquid lubricant, and besides gives no consideration to the roughness of magnetic disk medium and the texture of slider surface of the magnetic head and suffers from the problem that reliability of magnetic disk apparatus performing recording and reproduction at a small floatation distance cannot be ensured.
Moreover, the conventional technique disclosed in Japan Tribology Society, preliminary lecture collection, 1996-5 (page 50) gives no consideration to the optimization of lubricants of the corresponding magnetic disk media and suffers from the problem that reliability of magnetic disk unit performing recording and reproduction at a small floatation distance cannot be ensured.